Scale Tension in GCFT Coherence Coupling: Venus Ephemeris Bound vs. Andromeda Flyby Signal

CDN-139 demonstrated that the GCFT coherence coupling term F_c = −κ_c (v·r̂) r̂/r² shifts the Milky Way–Andromeda merger probability by more than 10% at κ_c ≥ 0.5×10⁵ kpc² Gyr⁻¹, with a distinctive flyby enhancement at κ_c = −0.5×scale. This paper applies the same coupling to the Venus–Jupiter system and derives the constraint imposed by existing planetary ephemeris precision (~10 m from VLBI and spacecraft ranging). The solar system allows κ_c at most 2.4×10⁻¹⁷ kpc² Gyr⁻¹. The gap between the galactic-scale signal and the solar-system bound is 4×10²¹. The scale-invariant coupling form cannot be universal. Three candidate resolutions are identified — density screening (analogous to chameleon/symmetron mechanisms), Yukawa-type spatial cutoff with coherence length λ_c, and mass-ratio power-law scaling — each with distinct near-term falsification conditions. The PSR J0740+6620 MeerKAT proposal (10.5281/zenodo.20375304, already submitted) is identified as the most immediate discriminant between the Yukawa and mass-ratio resolutions. No formal exclusion of GCFT is claimed; this is a structural consistency constraint the theory must satisfy to remain viable at both scales.